Currently 2G (GSM), 2.5G (GPRS) and 3G (UMTS/UTRA) mobile or cellular telecommunications network systems (PLMNs) co-exist. A development of the radio access network part of 3G mobile telecommunications is “evolved” UTRA or E-UTRA, also referred to as LTE (Long Term Evolution). “System Architecture Evolution” (SAE) is the development of the core network part of 3G mobile telecommunications. The combined core network and radio network development is sometimes referred to as SAE/LTE. It is desirable for mobile terminals to provide continuous service also when moving from a LTE coverage area to a 3G or 2G coverage area or vice versa from a 3G or 2G coverage area to a LTE coverage area.
To reduce signalling loads between a mobile device (UE: User Equipment) and the telecommunications network system while in idle state or idle mode, idle or inactive state signalling reduction, sometimes referred to as idle mode signalling reduction (ISR), is known. This is for example described in 3GPP TS 23.401, version 8.4.1 Release 8, which is fully incorporated herein by reference, see particularly Annex J: “High level ISR description”.
In view of the usage of IP based services, it is envisaged that EPS bearer contexts (EPS: Evolved Packet System) and/or PDP contexts (PDP: Packet Data Protocol) are constantly created, modified, and possibly returned to their original state. From point of view of a mobile device, even though there is no “net” change in the EPS bearer contexts and/or PDP contexts when entering and leaving a first Radio Access Technology (RAT), for instance UTRAN/GERAN, a location update in the other Radio Access Technology (second RAT), for instance E-UTRAN, may still be needed based on the principles of ISR.
This undermines the efficiency of using ISR and leads to, that a mobile device needs to make location updates every time it changes radio access technology (RAT), even if its EPS bearer contexts and/or PDP contexts have effectively not changed. As a result the signaling loads the network. Additionally the last of the battery of the mobile device is shortening.